Engine/Transmission (1998.5 - 2002) Mach 1.5's and Towing - Not what I expected.

[paulb]

oh, and for those who are still wondering why I compared the Horsepower of a gas engine and diesel running the same turbo... . it is all a matter of Air to Fuel Ratios... . a gas engine runs very well at 12:1-13:1 A diesel runs best at over 18:1 (smoke is very apperent at ratios less than 18:1).



If a turbo can make 400-450HP on a gas engine, it is basicly only good for 270-325 on a diesel (these are flywheel figures)

The af ratio is not the issue, because the weight of the fuels are not the same. An 18:1 af ratio means 18 pounds of air for each pound of fuel. Diesel is heavier (~7. 1lbs/gallon), than automotive gasoline (~6. 25 lbs/gallon), and diesel also has more btu's/per gallon. What would really matter is the amount of air required to produce a HP with each fuel, while running at a stoichiometric ratio. Add a little extra air for cooling in the diesel...



Paul

 

[PC12Driver]

Okay, turn off the calulator and put away your turbo maps for a sec, take a step back and look at the big picture.



Len's truck has enough fueling for about 350hp. He tows heavy. His observation is that his temps are too high for his comfort when pulling up long grades. The fact that he can hit 38psi, but he's only seeing 25psi on the pulls tells me that he's not at full throttle. The engine is probably only developing 200hp or less at that point, and is probably turning about 1800 rpm. He doesn't need full throttle, high rpm cooling. So forget the 350hp. It doesn't apply here.



Is the 'BG adequate for 200hp? Absolutely.



Would switching to a 12cm housing extract more energy from the exhaust stream compared to the 14cm? Yes.



More energy extracted from the exhaust gasses translates into more energy driving the compressor, which will result in more boost.



For the typical Dodge/Cummins application the 'BG is good to 40psi (per HTT). So any increase in boost from the 'BG, up to 40psi-ish, will result in beneficial boost (increase in psi = decrease in egt).



Will the 2cm decrease in housing cross section be restrictive enough (at 200hp and roughly 1800 rpm) to cause high egts? Not even close. A 450hp truck, full throttle, at 2700 rpm saw the same or lower egts by switching to the 12cm housing. That's the beauty of a small housing and a good wastegate.



Len is looking for mid-throttle, mid-rpm performance. Switching to a smaller housing will spool the turbo harder mid-throttle and will increase the air charge's density, which will decrease egts (providing he stays below 40psi, which isn't a problem with the full wastegate).



I've been in Len's exact same situation before. I added 200hp and my truck pulled worse than with just the EZ. I downsized the exhaust housing and started making boost earlier, where I needed it, and gained back my towing performance. My other example (the mechanic in the cornfield) told me he regularly has customers coming to him after they add an HX40 and wonder where the towing performance went. He tells them to put the stock turbo back on, and whaddaya know, it works every time. No calculators or maps needed on this one. I've been there, done that, hands-on. The guy in the cornfield has done way more research than either of us, and it works for him.



So what, in this post specifically, am I missing?





There's a reason there's test pilots; it's because engineers usually get it wrong on the first couple of attempts. There's no substitute for real world trial and error.

You can be impressed if you want... I know I am!!!

We can tell...

 

[PC12Driver]

Len, sorry about trashing your thread.



I know these trucks can pull with the fueling you have, since I've got a tad more and don't have a problem with egts while pulling the 5ver. I do believe that you can get more out of your turbo by swapping housings, but don't take my word for it. Give HTT a call and tell them honestly how you intend to use your truck. I'm betting that as soon as you say "tow", they'll suggest a smaller housing.



Keep us posted.

 

[lkuykendall]

Wow, this is the first chance that I have had to check the thread today and it looks like I have been missing out. I really appreciate the responses from everyone and have just about decided to order a 12 cm2 exhaust housing. I believe that PC12Driver has made a good point. I am turning less that 2000 rpm most of the time so I believe this is really limiting the air flow from this turbo with the 14 cm2 housing. To help confirm this I have noticed that if I bump the speed up to 70-75 which gets the rpm a little higher, I am topping the hills at a lower EGT. I personally don’t like pulling at that speed for obvious reasons but did test it on the last trip. Again, I really appreciate the feedback from everyone and feel free to keep it coming; I am still open for suggestions from others with first hand experience.



Len

 

[Gary - K7GLD]

The whole focus here as to turbo size, with or without related mods, SHOULD be to be aware of tradeoffs various add-ons might create - and then choose the mods that most often apply to your situation or needs... .



:I've been in Len's exact same situation before. I added 200hp and my truck pulled worse than with just the EZ. I downsized the exhaust housing and started making boost earlier, where I needed it, and gained back my towing performance. "



And all that is fine - AS LONG AS towing capability IS your primary interest, and max performance in non-towing circumstances up higher in the RPM/powerband is something you can live without...

 

[Diesel Freak]

The af ratio is not the issue, because the weight of the fuels are not the same. An 18:1 af ratio means 18 pounds of air for each pound of fuel. Diesel is heavier (~7. 1lbs/gallon), than automotive gasoline (~6. 25 lbs/gallon), and diesel also has more btu's/per gallon. What would really matter is the amount of air required to produce a HP with each fuel, while running at a stoichiometric ratio. Add a little extra air for cooling in the diesel...



Paul

Glad you brought that up.



since the air:fuel ratio is a ratio of masses consumed:



Lower heating values:



Gasoline: 20300 BTU/lb

Diesel: 19300 BTU/lb



Which fuel has a higher specific energy content?



looks like Gasoline to me.



Stoich for Gas is 14. 7:1 Diesel is 14. 5:1



Run a gas engine a little rich oh, 12:1 to 13:1 for reliability and best performance.



Run the Diesel lean to keep EGT low, and promote complete combustion... a minimum of 18:1 and WAYYYYYYYYYYYYYYYYY leaner... provided there is enough compression heat available for combustion



Yes, I know automotive diesel engines are more thermally efficient than a gasoline engine. But a diesel engine will still have to consume ~50% more air than a gasoline engine at the same power level. That is why I drop the gasoline power rating for a turbo by 1/3 to find it's capabilities when run on a diesel engine for 100% duty cycle.

 

[Diesel Freak]

Okay, turn off the calulator and put away your turbo maps for a sec, take a step back and look at the big picture.



Len's truck has enough fueling for about 350hp. He tows heavy. His observation is that his temps are too high for his comfort when pulling up long grades. The fact that he can hit 38psi, but he's only seeing 25psi on the pulls tells me that he's not at full throttle. The engine is probably only developing 200hp or less at that point, and is probably turning about 1800 rpm. He doesn't need full throttle, high rpm cooling. So forget the 350hp. It doesn't apply here.



Is the 'BG adequate for 200hp? Absolutely.



Would switching to a 12cm housing extract more energy from the exhaust stream compared to the 14cm? Yes.



More energy extracted from the exhaust gasses translates into more energy driving the compressor, which will result in more boost.



For the typical Dodge/Cummins application the 'BG is good to 40psi (per HTT). So any increase in boost from the 'BG, up to 40psi-ish, will result in beneficial boost (increase in psi = decrease in egt).



Will the 2cm decrease in housing cross section be restrictive enough (at 200hp and roughly 1800 rpm) to cause high egts? Not even close. A 450hp truck, full throttle, at 2700 rpm saw the same or lower egts by switching to the 12cm housing. That's the beauty of a small housing and a good wastegate.



Len is looking for mid-throttle, mid-rpm performance. Switching to a smaller housing will spool the turbo harder mid-throttle and will increase the air charge's density, which will decrease egts (providing he stays below 40psi, which isn't a problem with the full wastegate).



I've been in Len's exact same situation before. I added 200hp and my truck pulled worse than with just the EZ. I downsized the exhaust housing and started making boost earlier, where I needed it, and gained back my towing performance. My other example (the mechanic in the cornfield) told me he regularly has customers coming to him after they add an HX40 and wonder where the towing performance went. He tells them to put the stock turbo back on, and whaddaya know, it works every time. No calculators or maps needed on this one. I've been there, done that, hands-on. The guy in the cornfield has done way more research than either of us, and it works for him.



So what, in this post specifically, am I missing?

I agree... . now that we have settled on a lower specific power level.



A BG is definately adequate for 200 HP. If he can't get enough boost from it at that power level, then a smaller housing would help. It will just run a little hotter and drive pressure will be slightly higher WOT.

 

[hammersley]

Diesel Fuel has more BTU's than Gasoline!

Very interesting source for working.....



http://www.ext.colostate.edu/pubs/farmmgt/05006.html



Diesel fuel 7. 0 lb/gal* 138,000 Btu/gal*

Gasoline 6. 2 lb/gal 124,300 Btu/gal

LP gas 4. 25 lb/gal 92,300 Btu/gal



Table 1: Average rates of fuel consumption for year-round operation of three fuel-type tractors.



Engine fuel type Average fuel consumption per rated PTO-hp



Diesel fuel 0. 048 gal/hr

Gasoline 0. 068 gal/hr

LP gas 0. 080 gal/hr



Another source indicated... ... diesel fuel weighs more than gasoline and

since we buy fuel by the gallon, rather than by the pound or by its BTU content, a diesel gets more power out of a given volume of fuel.

 

[Diesel Freak]

Very interesting source for working.....



http://www.ext.colostate.edu/pubs/farmmgt/05006.html



Diesel fuel 7. 0 lb/gal* 138,000 Btu/gal*

Gasoline 6. 2 lb/gal 124,300 Btu/gal

LP gas 4. 25 lb/gal 92,300 Btu/gal



Another source indicated... ... diesel fuel weighs more than gasoline and

since we buy fuel by the gallon, rather than by the pound or by its BTU content, a diesel gets more power out of a given volume of fuel.

according to the above data

Diesel 19714 BTU/lb

Gasoline 20048BTU/lb



I rest my case.

 

[hammersley]

Who buys

fuel by the pound? Which is denser? And from an economic standpoint at equal $$$$/gallon - who is getting more BTU's/$$$$?

 

[Diesel Freak]

fuel by the pound? Which is denser? And from an economic standpoint at equal $$$$/gallon - who is getting more BTU's/$$$$?

We were talking with respect to the mass of air and fuel consumed, not the ammount of cash given to Al-Quaida

 

[paulb]

Engine fuel type Average fuel consumption per rated PTO-hp



Diesel fuel 0. 048 gal/hr

Gasoline 0. 068 gal/hr

LP gas 0. 080 gal/hr

Very good. You've got it! Seeing as how we are talking about how much air is need per hp, those figures are the important ones. It takes ~ 30% less volume of diesel to make one hp, or ~21% less lbs. of diesel. By Cliffs figures of 18:1 and 12. 5:1 (though this is kinda comparing apples to oranges, because you are using the best power ratio of gas, and the best durablity for diesel), that is ~ 31% difference. So as far as how much air is need to make a hp, diesel needs about 10% more. This is with the diesel running 18:1. If it was running at stoic, then the diesel would need ~20% less. So pick your number!



Good job on the research hammersley!



Paul

 

[PC12Driver]

I agree... . now that we have settled on a lower specific power level.



A BG is definately adequate for 200 HP. If he can't get enough boost from it at that power level, then a smaller housing would help. It will just run a little hotter and drive pressure will be slightly higher WOT.

There's no "we" in this. I was taking it from the towing point of view to begin with.



And if you follow the links that I posted earlier, you'll see that dropping from a 14 to a 12 (also on an HTBG) resulted in the same or less egts at WOT. Those are real world numbers measured pre-turbo with an SPA digital gauge. Nothing theoretical here. I would have said the same thing about a smaller housing until I saw those results. I guess that shows what a good wastegate will do for you.

 

[RJPotts]

I'm with PC12Driver and everyone else that said hammer down on it a little more.

Granted the more boost you make, and the longer you're under boost you get higher cylinder pressures, which is more wear and tear, but its hard to kill a Cummins.

1300*F pre turbo is still a fairly "safe" temperature for a few seconds, I wouldn't keep it there all day but its not gonna hurt anything. Keep your RPM up and give 'er h*ll.

-R. J.

 

[Diesel Freak]

Very good. You've got it! Seeing as how we are talking about how much air is need per hp, those figures are the important ones. It takes ~ 30% less volume of diesel to make one hp, or ~21% less lbs. of diesel. By Cliffs figures of 18:1 and 12. 5:1 (though this is kinda comparing apples to oranges, because you are using the best power ratio of gas, and the best durablity for diesel), that is ~ 31% difference. So as far as how much air is need to make a hp, diesel needs about 10% more. This is with the diesel running 18:1. If it was running at stoic, then the diesel would need ~20% less. So pick your number!



Good job on the research hammersley!



Paul

AH, now I see it. I was holding fuel flow rates constant.



for the same power level, a diesel could have a fuel flow rate of . 336 lb/hr where a gas could have a flow rate of . 422 lb/hr



now going back to my apples to oranges assumption with air:fuel ratios



With engines of the same power output, a diesel would consume 15% more air at 18:1



I stand corrected!!!

 

[paulb]

AH, now I see it. I was holding fuel flow rates constant.



for the same power level, a diesel could have a fuel flow rate of . 336 lb/hr where a gas could have a flow rate of . 422 lb/hr



now going back to my apples to oranges assumption with air:fuel ratios



With engines of the same power output, a diesel would consume 15% more air at 18:1



I stand corrected!!!

Yep, you got it!



It would be interesting to see how close the 18:1 guess is... My guess is that for max hp it would be closer to 16:1, but the EGT's would be high. It's all about thermal efficency!



Paul

 

[Diesel Freak]

Yep, you got it!



It would be interesting to see how close the 18:1 guess is... My guess is that for max hp it would be closer to 16:1, but the EGT's would be high. It's all about thermal efficency!



Paul

yeah, it might be a bit toasty.



I would like to be closer to 20:1, just for the EGT relief, and essentially non-existent smoke. Some power may be lost from pumping loss, but that is ok with me.

 

[JJ Jackson]

hmmm



Hey Vaughn, now I know why a lot of the informed posters on this board have left.

Diesel Freak, come on, think about what you say before you post.

Alot of us post real world info about things that we personally expierience. It may conflict with mathmatical equations sometimes, but it should not be taken with a grain of salt.



I know that the simplest response to Lukes question would be "If you don't like high exhaust temps then get twins". But thats not the answer he's looking for. He want's to know how to make his current set-up work at no more than 1100*



Can you put your info in terms we all can understand? Does WOT performance with a bigger turbo mean that it works better than stock but only in high rpm situations? What I mean is, lets take a stock HX12 and lets say I have it WOT at 1800 rpm and EGT is 1200. Now WOT at 2800rpm is 1350. Does this mean that 2800rpm is past the efficiency range of the HX12?



Now lets take the same scenario with a bigger turbo. What is the WOT EGT at 1800rpm, 2800 rpm?



WOT at different rpm's and can cause differnt EGT's with different size turbos, right?



So I know from personal expierience that I can hold my engine at 2200 rpm with a stock HX12 at WOT and not get it any hotter than 1250*. But if I downshift and hold WOT at 2800rpm it will easily hit 1300*. Obviously my stock HX12 can't maintain cool EGT at that rpm.



So, do I throw my HX12 out in get a big single get better high rpm power and have some driveability issues around town, or do I simply adjust my driving style to my pyro and keep what I have.



And for the record low EGT's don't always mean you are resistant to piston seizure, high coolant temp, high rpm and lack of oil flow can also play in.



I don't drive around feathering the throttle to maintain 1300*, but I also don't let it scare me when I'm towing. When I have a Ford coming up on my left, I'm not about to let off. Those are the only times I would hold those kind of EGT's.



I bombed this truck because I have a competitive spirit, and I would not drive it any other way. So, Luke, don't let 1000* hold you back.



Diesel Freak, don't mean to flame you, just trying to make sense of this all for us "un-informed" guys. :-laf ... . Jim

 

[Diesel Freak]

Diesel Freak, don't mean to flame you, just trying to make sense of this all for us "un-informed" guys. :-laf ... . Jim

no worries



I prolly should define things in laymans terms more frequently.



but if you look through this thread... . even I get schooled at times.

 

[Clmsnow]

Wow... . haven't been on here in awhile and look what I missed!! I have the HTBG and LOVE it. I started with the 14cm housing and noticed it was a little slow to wind up and my EGT's at 7000ft on an incline were high. Around town the EGT's were ok, but I was only getting about 34-35psi with my Comp on 5x5. I spoke with many about the problem and upgraded(or downgraded ) to the 12cm housing. Gained a little more psi(boost) at elevation and because of this my EGT's dropped. I noticed it was quicker to wind up. Talked to HTT some more and they told me the turbo was most effecient around 40psi and that I could adjust this with the actuator rod. I did this and started seeing 40psi with the Comp on 5x5. At the same time, I also noticed the truck had about the same lag as the stock HY turbo(which was a good thing) and the EGT's lowered again. I don't want to get into an arguement with anyone, just report my findings. On a flat stretch, with my Comp on 5x5, I can run my truck up to 100mph and see 40psi boost and 1320*EGT. Not bad in my humble opinion. Obviously in the hills or towing the EGTs are higher, but then again, I usually don't run the Comp on kill. I have been happy with the turbo... . REALLY happy, regardless of what anyone says!!